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From: Tejun Heo <tj@kernel.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Roland McGrath <roland@hack.frob.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Pedro Alves <palves@redhat.com>,
	Jan Kratochvil <jan.kratochvil@redhat.com>
Subject: Re: [PATCH 1/2] ptrace: make wait_on_bit(JOBCTL_TRAPPING_BIT) in ptrace_attach() killable
Date: Mon, 23 Nov 2015 18:05:52 -0500	[thread overview]
Message-ID: <20151123230552.GJ19072@mtj.duckdns.org> (raw)
In-Reply-To: <20151119184732.GB19061@redhat.com>

On Thu, Nov 19, 2015 at 07:47:32PM +0100, Oleg Nesterov wrote:
> ptrace_attach() can hang waiting for STOPPED -> TRACED transition if the
> tracee gets frozen in between, change wait_on_bit() to use TASK_KILLABLE.
> 
> This doesn't really solve the problem(s) and we probably need to fix the
> freezer. In particular, note that this means that pm freezer will fail if
> it races attach-to-stopped-task.
> 
> And otoh perhaps we can just remove JOBCTL_TRAPPING_BIT altogether, it is
> not clear if we really need to hide this transition from debugger, WNOHANG
> after PTRACE_ATTACH can fail anyway if it races with SIGCONT.
> 
> Reported-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun

  reply	other threads:[~2015-11-23 23:05 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-09 15:12 ptrace() hangs on attempt to seize/attach stopped & frozen task Andrey Ryabinin
2015-11-09 18:55 ` Oleg Nesterov
2015-11-09 18:02   ` Tejun Heo
2015-11-10 20:20     ` Oleg Nesterov
2015-11-16 18:45       ` Tejun Heo
2015-11-17 19:34         ` Oleg Nesterov
2015-11-17 18:57           ` Tejun Heo
2015-11-19 16:49           ` Pedro Alves
2015-11-19 17:47             ` Oleg Nesterov
2015-11-19 18:08               ` Pedro Alves
2015-11-10 20:20   ` Oleg Nesterov
2015-11-19 18:47 ` [PATCH 0/2] (Was: ptrace() hangs on attempt to seize/attach stopped & frozen task) Oleg Nesterov
2015-11-19 18:47   ` [PATCH 1/2] ptrace: make wait_on_bit(JOBCTL_TRAPPING_BIT) in ptrace_attach() killable Oleg Nesterov
2015-11-23 23:05     ` Tejun Heo [this message]
2015-11-19 18:47   ` [PATCH 2/2] ptrace: task_stopped_code(ptrace => true) can't see TASK_STOPPED task Oleg Nesterov
2015-11-23 23:15     ` Tejun Heo

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